As a semiconductor device in which a semiconductor chip including an integrated circuit is sealed with a resin, for example, a so-called TSOP (Thin Small Outline Package) type semiconductor device is known. As this TSOP type semiconductor device, a device in which an LOC (Lead On Chip) structure which is prevented from including a die pad (in other words, tab) of a lead frame and is applicable to also a large size semiconductor chip is used, is known.
The TSOP type semiconductor device with LOC structure includes a semiconductor chip, a plurality of leads adhesively fixed to a circuit forming surface of a main surface of the semiconductor chip through an insulating film (an insulating tape), a plurality of bonding wires (metallic thin wires) connecting electrically respective electrodes on the circuit forming surface of the semiconductor chip to the leads respectively, and a resin sealing body for sealing the semiconductor chip, the leads, the bonding wires and so forth. The leads include inner leads arranged in the resin sealing body and outer leads extending from the inner leads and arranged at the outside of the resin sealing body. The outer leads are bent to have a gull-wing shape as a lead shape of surface mounting type.
In a production of the TSOP type semiconductor device with LOC structure, firstly a semiconductor wafer including a plurality of chip formed areas is divided by dicing to the semiconductor chips, and subsequently the semiconductor chips is fixed to a lead frame. The semiconductor chip is fixed to the lead frame by adhering the inner leads of the lead of the lead frame to the circuit forming surface of the semiconductor chip through the insulating film.
Subsequently, the electrodes of the circuit forming surface of the semiconductor chip are electrically connected to the inner leads of the lead of the lead frame by the bonding wires, and subsequently, the semiconductor chip, the inner leads of the lead, the bonding wires, suspending leads and so forth are sealed with the resin to form the resin sealing body. The sealing with the resin is performed through a transfer-molding process preferable for mass production. For example, an epoxy type thermosetting resin including a phenol type setting agent, a silicone rubber, a filler and so forth is used as the resin. A resin sealing temperature (temperature at which the thermosetting is performed) is about 180° C.
Subsequently, a post cure of about 5 hours is performed at a temperature substantially equal to the resin sealing temperature to stabilize the curing reaction of the thermosetting resin.
Subsequently, the outer leads of the lead are separated from the frame body of the lead frame, unrequired portions are removed from the lead frame, subsequently the outer leads of the lead is formed to have a predetermined shape (for example, the gull wing shape), and subsequently the suspending leads are separated from the frame body of the lead frame. Finally, an external appearance of a package including the outer leads and the resin sealing body is inspected and a characteristic thereof as a finished product is inspected to judge whether or not it is good. In the inspection of the characteristic thereof, for example, an aging test of about 16 hours at 90° C. is performed. The aging test is a screening test in which the circuit is operated at an operating condition (with an additional load) more severe than an operating condition of an user to accelerate an occurrence of defect which will be elicited in the operation of the user so that a defective one is eliminated at an initial step before being supplied to the user.
In the above production, since the sealing (molding) with the resin is performed at a high temperature, the resin contracts in a cooling step to a room temperature so that a compressive stress is generally generated in the semiconductor chip.